The invention generally relates to an actuator module to operate a downhole tool.
A testing or production system for a subterranean well may include various downhole tools that are remotely operated from the surface of the well. As examples, these tools may include a flapper valve, a ball valve, a sleeve, a packer, etc.
The downhole tool may operate in response to a fluid pressure. More specifically, a conventional pressure-operated downhole tool operates in response to a fluid pressure that exists either in a passageway of a tubing string (containing the downhole tool) or in the annulus of the well (that surrounds the tool). The fluid pressure may be a function of the weight of the column of fluid that extends to the surface of the well as well as any additional pressure that may be applied to the column from the surface of the well.
Several different pressure-operated downhole tools may be present in the well, and it may be desirable to selectively operate these tools at different times to perform different downhole functions. Different conventional techniques may be used to prevent a particular pressure-operated downhole device from operating until desired. For example, each pressure-operated downhole tool may respond only when the fluid pressure exceeds a particular pressure level. Thus, one particular downhole tool may only respond to the fluid pressure when the pressure exceeds some predetermined threshold, another downhole tool may respond when the fluid pressure exceeds a higher predetermined threshold, etc.
To achieve this type of pressure sensitive operation, a particular downhole tool may include a rupture disc to establish a barrier between the fluid pressure (present in a passageway of a tubing string or in an annulus of the well) and a piston head of an operator mandrel of the tool. When the fluid pressure exceeds a predetermined level, the rupture disc ruptures to permit the fluid pressure to act on the piston head to move the operator mandrel to actuate the downhole tool.
A potential challenge associated with the above-described control scheme is that the number of pressure-operated downhole tools in a particular well may be limited due to the limitations on the tubing pressure rating or surface pressure.
Another control scheme for selectively controlling downhole tools includes the communication of pressure pulses downhole. The identification of a particular downhole tool as well as a command (an “open valve” command, for example) for that tool may be encoded in these pressure pulses. A binary pattern of high and low pressure pulses may be used to distinguish a particular command or uniquely identify a particular downhole tool, as compared to controlling the tools using different pressure levels. Therefore, the pressure pulse-type control scheme remains within pressure ratings regardless of the number of downhole tools. However, a potential challenge with this arrangement is that downhole tools that decode and respond to the pressure pulses typically may be complex in design and are relatively expensive to make. Tools having other types of remote actuation (e.g., acoustic actuation) suffer from similar challenges.
Thus, there is a continuing need for an arrangement and/or technique that addresses one or more of the problems that are set forth above as well as possibly address one or more additional or different problems that are not set forth above.